The bivalve mollusc hinge ligament will be studied by structural and chemical techniques as a model biological system and as a potential source of material for human bone and teeth reconstruction. Preliminary work shows the ligament of Spisula solidissima to be composed of an array of sheathed aragonite crystals aligned in a complex protein matrix. The crystals are approximately 800 angstrom units in diameter and several thousand angstroms long, extending perpendicular to the frontal growth interface of the ligament. The protein is a high glycine, cross- linked fibrous matrix consisting of helical strands in which the calcium carbonate is embedded. The frontal portion of the ligament, near the animal mantle, exhibits a system of protein sleeves containing an electron dense, amorphous material containing calcium. This material may be the site of initiation of calcification and thus represents a significant finding in the solution to the problem of tissue calcification. The structure of the ligament of S. solidissima and other mulluscs will be done using high an low angle x-ray diffraction, laser diffraction, scanning and transmission electron microscopy and electron probe analysis. Chemical studies will be initiated as indicated by the results of these structural studies.